Camshaft adjuster

ABSTRACT

A camshaft adjuster ( 1 ) is provided with a restoring spring ( 4 ) having a spring end ( 6 ) for support on the driven element ( 3 ) that has a wavelike shape.

INCORPORATION BY REFERENCE

The following documents are incorporated herein by reference as if fully set forth: German Patent Application No. 102012200683.4, filed Jan. 18, 2012.

FIELD OF THE INVENTION

The invention relates to a camshaft adjuster.

BACKGROUND

Camshaft adjusters are used in internal combustion engines for varying the timing of combustion chamber valves, in order to vary the phase relation between a crankshaft and a camshaft in a defined angular range between a maximum advanced position and a maximum retarded position. Adjusting the timing to the current load and rotational speed lowers consumption and emissions. For this purpose, camshaft adjusters are integrated into a drive train by which torque is transmitted from the crankshaft to the camshaft. This drive train can be formed, for example, as a belt, chain, or gearwheel train.

In a hydraulic camshaft adjuster, the driven element and the drive element form one or more pairs of pressure chambers that act opposite each other and can be charged with hydraulic medium. The drive element and the driven element are arranged coaxially. By filling and emptying individual pressure chambers, a relative movement is created between the drive element and the driven element. The rotationally acting spring between the drive element and the driven element forces the drive element in a preferred direction opposite the driven element. This preferred direction can be in the same direction or in the opposite direction relative to the direction of rotation.

One type of hydraulic camshaft adjuster is the vane cell adjuster. The vane cell adjuster has a stator, a rotor, and a drive wheel with external teeth. The rotor is constructed as a driven element that can be locked in rotation usually with the camshaft. The drive element includes the stator and the drive wheel. The stator and the drive wheel are locked in rotation with each other or are constructed, as an alternative, integrally with each other. The rotor is arranged coaxial to the stator and within the stator. With their radially extending vanes, the rotor and the stator form oppositely acting oil chambers that can be charged by oil pressure and allow a relative rotation between the stator and the rotor. The vanes are either formed integrally with the rotor or the stator or arranged as “inserted vanes” in grooves provided for this reason in the rotor or the stator. Furthermore, the vane cell adjusters have various sealing covers. The stator and the sealing covers are secured with each other by means of multiple threaded connections.

Another type of hydraulic camshaft adjuster is the axial piston adjuster. Here, a displacement element that generates a relative rotation between a drive element and a driven element via helical gearing is displaced in the axial direction by oil pressure.

Another construction of a camshaft adjuster is the electromechanical camshaft adjuster that has a triple shaft gear (for example, a planetary gear). Here, one of the shafts forms the drive element and a second shaft forms the driven element. Through the use of the third shaft, rotational energy can be fed to the system or output from the system by a control device, for example, an electric motor or a brake. There can also be a spring that increases or decreases the relative rotation between the drive element and the driven element.

JP 2003 120 229 shows different possibilities for supporting the spring ends of a restoring spring, in particular, of the radial outer spring end. In all of diagrams, the radial inner spring end is formed as a hook that is bent away from the rotational axis of the camshaft adjuster and is suspended on the driven element.

DE 10 2006 002 993 A1, DE 10 2008 051 142 A1, and DE 10 2008 051 755 A1 disclose camshaft adjusters with a restoring spring, wherein the radial inner spring end is bent by approx. 180° and is supported on a pin that is locked in rotation with the driven element.

SUMMARY

The object of the invention is to provide a camshaft adjuster that has a particularly reliable spring support.

This objective is met with a camshaft adjuster having one or more features of the invention.

For meeting this objective, a camshaft adjuster is provided that has a drive element and a driven element and also a restoring spring, wherein the mentioned components are arranged coaxial to the rotational axis of the camshaft adjuster, wherein the restoring spring generates a relative rotation of the drive element relative to the driven element, and wherein, according to the invention, the spring end of the restoring spring that is provided for support on the driven element has a wavelike shape.

Due to the wavelike shape of the spring end that is provided for support on the driven element, it is achieved that, for one, especially for a radial winding body, packaging space is saved and the load on the spring wire in the area of the spring support is reduced in contrast to a hook-shaped spring end known in the prior art. Advantageously, the bending radius of the spring end can align with the spring support such that an improved contact is achieved and Hertzian contact pressure is reduced.

There are predominantly two types of restoring springs. The two types of restoring springs are, on one hand, those with radial winding bodies and, on the other hand, those with axial winding bodies. The wavelike spring end is to be formed in both types of restoring springs. The restoring springs with radial winding bodies are advantageously to be used in axially limited packaging spaces, wherein, in contrast, the restoring springs with axial winding bodies are to be used in radially limited packaging spaces.

A wavelike spring end characterizes itself with the general understanding of a “wave,” that is, with at least one wave peak or at least one wave valley. Wave peaks and wave valleys can be arranged one after the other in rows in arbitrary frequency and can have different or equal amplitudes. A wave peak is viewed here as the amplitude away from the rotational axis of the camshaft adjuster, wherein analogously a wave valley is to be viewed as the amplitude toward the rotational axis of the camshaft adjuster. The amplitude itself is to be considered as the radial deviation from the imaginary extension in the continuing course of the winding, as much as possible in the direction of the wire extension.

With advancing angle around the rotational axis, the starting and end points of a wave decrease, approaching the same reference circle. Alternatively, it is possible to arrange the end point of a wave on a reference circle that is different from the starting point.

In one construction of the invention, the support point on the driven element has a shape that is complementary to the wave shape of the spring end. Advantageously, the complementary shape to the wave shape is formed such that an optimum osculation is achieved between the spring end and support and Hertzian contact pressure is significantly reduced. The complementary shape can be formed on the driven element itself, ideally in the area of its hub, or on a component locked in rotation with the driven element. The spring end is advantageously supported on the complementary support point, biased in the radial direction. Alternatively, the radial biasing can be eliminated.

In one advantageous construction, the support point is formed as part of a hub of a spring cover locked in rotation with the driven element. The spring cover protects the windings of the restoring spring from environmental influences and prevents that parts of a broken spring from being able to move into the internal combustion engine in the event of the breaking of a spring. The spring cover is advantageously formed as a thin-wall component with a hub. The hub is locked in rotation coaxially with the driven element.

In one particularly preferred construction, the spring cover is formed from sheet metal. The support point for the spring end can be shaped into the spring cover made from sheet metal by deep drawing, bending, stamping, or other shaping processes. Alternatively, the spring cover could be formed from a plastic and the support point could be produced, e.g., by casting or other shaping processes. The complementary support point can also be arranged as a separate component on the spring cover made from sheet metal by means of positive-fit, non-positive-fit, and/or material-fit connection techniques.

In one construction of the invention, the support point is formed integrally with the spring cover and is shaped away from the rotational axis of the camshaft adjuster. Thus, the support point of the construction of a wave peak corresponds analogously to that of the wave peak of the spring end. The formation of the support point on the spring cover as a wave peak is advantageous, so that, on the components arranged within the hub, no other modifications can be performed and the hub can have a very thin shape.

As an alternative, the construction of a wave valley has the advantage that, especially for a restoring spring with a radial winding body, the radial packaging space is better used for the next winding and the entire winding body can be housed in a smaller radial packaging space.

In one preferred construction, the spring cover has a retaining tab that fixes the spring end in the radial direction. The retaining tab is provided on the support point as a counter holder of the wavelike spring end, in order to increase the security of the contact between the spring end and support point. Advantageously, slippage of the spring end from the support point, caused, e.g., by vibrations of the internal combustion engine, is counteracted in this way. The retaining tab fixes the spring end in the radial and/or peripheral direction in a positive-fit connection. Multiple retaining tabs on the spring cover can flank a wave peak of the spring end or can be arranged centrally relative to a wave valley of the spring end.

In another construction of the invention, the retaining tab is formed integrally from the spring cover. In particular, a construction of the spring cover made from sheet metal is advantageous with respect to economy and reliability or service life. Alternatively, such retaining tabs can be cast on a spring cover made from metal or plastic.

In one advantageous construction, the support point or the retaining tab of the spring cover is provided for the angular positioning of the spring cover relative to the driven element. By use of the support point or the retaining tab, a positive-fit connection of the spring cover relative to the driven element can be simultaneously formed that guarantees a reliable orientation of the driven element relative to the spring cover and thus also relative to the restoring spring and thus ensures a reliable construction of the desired spring moment between the driven element and the drive element.

In another construction of the invention, a spring cover is locked in rotation with the driven element, wherein the driven element can be connected, in turn, with a camshaft and the spring cover is formed simultaneously as a trigger wheel. Especially for restoring springs with radial winding bodies, these are advantageously arranged on an end face of the camshaft adjuster and covered by the spring cover. A trigger wheel function by formed notches or other markings on the spring cover presents itself advantageously and can be achieved easily by an angular position sensor. By the use of a central screw/nut, spring covers with trigger wheel functions, driven elements, and camshafts can be locked in rotation with each other.

A reliable and low-tension connection of the restoring spring to the driven element is achieved by the construction according to the invention of the spring end for support on the driven element in a wavelike shape.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are shown in the figures.

Shown are:

FIG. 1 is a view of a camshaft adjuster with a restoring spring according to the prior art,

FIG. 2 is a view of a camshaft adjuster with the construction of the spring end and its support point according to the invention, and

FIG. 3 is a view of the spring cover and the restoring spring of the camshaft adjuster according to FIG. 2 in an additional view.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a camshaft adjuster 1 with a restoring spring 4 according to the prior art. The function and the construction of a hydraulic camshaft adjuster 1 with the arrangement of drive element 2 and driven element 3 in its construction as a vane-cell adjuster or as an axial piston adjuster is known from the prior art and explained sufficiently in the introduction. The support point 7 is formed as a pin and locked in rotation with the driven element 3. The restoring spring 4 has a radial winding body, i.e., the windings line up in the radial direction. The spring end 6 that is supported on the support point 7 has a hook-shaped construction. The hook was bent from the imaginary extension of the wire of the restoring spring 4 radially inward, that is, toward the rotational axis 5, by approximately 90° and extends around the support point 7. The inner radius of the hook of the spring end 6 is approximately equal to the radius of the pin of the support point 7.

Analogous to the inner spring end 6, the outer spring end 12 of the restoring spring 4 is supported on a support point 11, wherein the support point 11 is locked in rotation with the drive element 2. The spring end 12 was bent approximately by 180°. The inner radius of the spring end 12 is approximately equal to the radius of the support point 11.

FIG. 2 shows a camshaft adjuster 1 with the wavelike construction according to the invention of the spring end 6 and its support point 7. The spring cover 9 is arranged coaxial to the rotational axis 5 of the camshaft adjuster 1. The spring cover 9 has a hub 8 and a ring disk 13 constructed integrally on this hub. The spring cover 9 is constructed as a thin-wall sheet metal part and locked in rotation with the driven element 3. The ring disk 13 of the spring cover 9 extends in the radial direction and covers a part of the winding body of the restoring spring 4. The ring disk 13 has two retaining tabs 10 and a support point 7. The retaining tabs 10 are oriented relative to the drive element 2 or the driven element 3 and machined integrally from the sheet metal part. The support point 7 is constructed as a bead from the outer diameter of the hub 8 and oriented away from the rotational axis 5 of the camshaft adjuster 1. The two retaining tabs 10 flank the support point 7.

The construction of the outer spring end 12 of the restoring spring 4 corresponds to the construction of the outer spring end 12 according to FIG. 1.

FIG. 3 shows the spring cover 9 and the restoring spring 4 of the camshaft adjuster 1 according to FIG. 2 in another view. This view shows the side of the spring cover 9 that is hidden in FIG. 2. With the now free view onto the wavelike spring end 6 it is easily visible that the spring end 6 is constructed as a wave peak. The start and end of the wave peak are located as much as possible on the same reference circle. The support point 7 constructed as a bead projects in its axial extent past the wire thickness of the restoring spring 4. The retaining tabs 10 are bent at an angle of approximately 90° away from the ring disk 13.

If the spring end 12 is now deflected so that the winding body is tensioned, the retaining tabs 10 prevent slippage of the spring end 6 past the support point 7 in the peripheral direction. Due to the feasibility of a larger osculation between the spring end 6 and support point 7 due to larger radii in the contact point, the tension load on the spring end 6 is minimized.

In addition, the spring cover 9 has an integral flange 14 connected to its hub 8. With this flange 14, the spring cover 9 can be locked in rotation via a central threaded connection, coaxial to the rotational axis 5, with the driven element 3 and a camshaft. The support point 7 and/or the positive-fit element 15 are provided for the angular-oriented fixing of the spring cover 9 relative to the driven element 3. The support point 7 and/or the positive-fit element 15 engage in complementary receptacles of the driven element 3. Advantageously, the support point 7 and the positive-fit element 15 have the same shape, but are arranged in a pattern for the clear angular positioning between the spring cover 9 and driven element 3 on the periphery of the hub 8. The spring cover 9 can be centered relative to the driven element 3 by means of the hub 8, especially with its outer diameter.

LIST OF REFERENCE NUMBERS

-   1) Camshaft adjuster -   2) Drive element -   3) Driven element -   4) Restoring spring -   5) Rotational axis -   6) Spring end -   7) Support point -   8) Hub -   9) Spring cover -   10) Retaining tab -   11) Support point -   12) Spring end -   13) Ring disk -   14) Flange -   15) Positive-fit element 

1. A camshaft adjuster comprising a drive element, a driven element, and also a restoring spring which are arranged coaxial to a rotational axis of the camshaft adjuster, the restoring spring generates a relative rotation of the drive element relative to the driven element, and a spring end of the restoring spring that is provided for support on the driven element has a wavelike shape.
 2. The camshaft adjuster according to claim 1, wherein a support point for the spring end on the driven element has a shape that is complementary to the wavelike shape of the spring end.
 3. The camshaft adjuster according to claim 2, wherein the support point is formed as part of a hub of a spring cover that is locked in rotation with the driven element.
 4. The camshaft adjuster according to claim 3, wherein the spring cover is formed from sheet metal.
 5. The camshaft adjuster according to claim 3, wherein the support point is formed integrally with the spring cover and shaped away from the rotational axis in the radial direction.
 6. The camshaft adjuster according to claim 3, wherein the spring cover has a retaining tab that fixes the spring end in a radial direction.
 7. The camshaft adjuster according to claim 6, wherein the retaining tab is formed integrally from the spring cover.
 8. The camshaft adjuster according to claim 6, wherein the support point or the retaining tab of the spring cover is provided for angular positioning of the spring cover relative to the driven element.
 9. The camshaft adjuster according to claim 1, wherein a spring cover is locked in rotation with the driven element, the driven element is connectable with a camshaft, and the spring cover is simultaneously formed as a trigger wheel.
 10. A restoring spring of a camshaft adjuster according to claim
 1. 